Purdue researchers develop biofuel process

Researchers at Purdue University in Indiana are developing a new biofuel processing system based on fast hydropyrolysis, followed by catalytic hydrodeoxygenation. But for short, they call it H2Bioil.

In a fast-hydropyrolysis reactor, solid biomass is rapidly heated to temperatures of about 900 degrees Fahrenheit in the presence of hydrogen, breaking down the complex molecules of the biomass into smaller molecules. Then the oxygen in those smaller molecules is removed through a reaction with hydrogen and the resulting molecules are the high-energy density oil molecules, according to Rakesh Agrawal, researcher and professor of chemical engineering at Purdue. "The quality of biofuel produced using H2Bioil is estimated to be two to three times the output from conventional processes," he said. The researchers are currently undertaking the task of developing their idea into a product and have published their findings in a research paper in the online journal Environmental Science & Technology. Ideally, the system would process agricultural biomass in the Midwest, but can take any type of biomass, Agrawal said.

"Biomass grown on land and subsequently converted to biofuel offers a solution to meet the large demand for liquid fuels," he said. "However, the limited land available to grow biomass in a sustainable manner implies that in order to meet the large demand, the available biomass must be efficiently converted to biofuel."

It's typical during biofuel production to lose one-third to one-half the carbon atoms in the biomass as carbon dioxide to meet the processing energy requirements, Agrawal said. The use of supplemental energy forms like hydrogen along with biomass ensures that the majority of the carbon atoms are preserved, resulting in a biofuel of better quality.

In a step to make the process more attractive in the short term, the team has proposed synergistic integration of H2Bioil with a small-scale steam methane reformer. In the integrated process, reformed methane will directly provide hot hydrogen gas for the fast-hydropyrolysis step, according to Agrawal. "This integration is not only synergistic in improving the process yield, but should also enable the construction of small-scale mobile plants," he said. That would alleviate expensive feedstock transportation costs, which are much higher than costs of transporting liquid fuel, according to the researchers.

The team is currently conducting experiments to demonstrate and improve understanding of the H2Bioil method and Agrawal expects the synergistic interaction with methane reforming to be commercially available within the next five years.

"As an efficient method of producing biofuels, the commercialization of H2Bioil would greatly advance the use of renewable fuels for transportation and reduce the dependency on oil from fossil fuel," Agrawal said. "By offering a means of converting the residual waste from agriculture into a valuable liquid fuel, H2Bioil, capable of being built on a small scale, has the potential to provide an economic boost to the farm sector as well."